PROJECT SUMMARY The Surgical Idiopathic Intracranial Hypertension Treatment Trial (SiihTT ? pronounced ?Sight?) is a randomized, controlled trial comparing medical and surgical therapies ? optic nerve sheath fenestration and stereotactic ventriculoperitoneal cerebrospinal fluid shunting in 180 subjects with idiopathic intracranial hypertension (IIH) with moderate and severe visual loss. The Study Steering Committee (SSC) is integrated into the Neuro-Ophthalmology Research Disease Investigator Consortium (NORDIC), utilizing the services of the Rochester Data Coordination and Biostatistical Center (DCBC); and the Photographic, Visual Field, and Optical Coherence Tomography Reading Centers, coordinated by a Resource Center. NORDIC will provide an Enrollment Center (EnrC) and Regional Monitors to assist the Site Investigators, Coordinators and Surgeons at 41 clinical sites throughout the U.S. and Canada. These entities will work together to adhere to the study protocol, complete the study and aid in manuscript preparation and results dissemination. The SSC, chaired by the Study Director. will be responsible for the major decisions and oversight of the SiihTT, including significant Clinic Site investigator or protocol issues and potential ancillary studies. We will complete and coordinate the Protocol and Manual of Procedures changes recommended by reviewers and the Data and Safety Monitoring Board. During the study, we will ensure SiihTT study data integrity, protocol fidelity and completion. We have established, three important committees will address the outcomes and safety issues under the direction of the SSC. These include: 1) Adjudication Committee; 2) Surgical Quality Assurance Committee; 3) Surgical Malfunction Review Committee. We will also mentor two early career Neuro- Ophthalmology investigators with experience in the conduct of clinical trials for future NORDIC trials. We will use the NORDIC network with its infrastructure, developed during the Idiopathic Intracranial Hypertension Treatment Trial, and its experienced study leadership, 41 sites, DCBC, Reading Centers, and EnrC to coordinate and complete the SiihTT.